1. Field of the Invention
The present invention relates to an optical functional waveguide, an optical modulator, an arrayed waveguide grating and a dispersion compensation circuit having a small size, used with saved energy and capable of controlling the phase of light at high speed and of adjusting the optical path length or wavefront.
2. Description of the Related Art
A conventional quartz waveguide type optical modulator is constituted so as to include a phase modulating portion, which provides a heater in the vicinity of an optical waveguide and varies the refractive index of quartz by heating, in the interference system. Because a reflective index temperature coefficient of the quartz, 1.1×10−5[1/° C.], is low in this constitution, a waveguide length (heater length) of about 970μ is required even if a temperature change of 50° C. is allowed in order to cause the phase change of π in a communication wavelength of 1.55μ band. A time required for the temperature change is several 10 ms, and energy required for the temperature rise becomes 100 mW or more. Thus, there remains an additional problem such as an increase in crosstalk by thermal interference between modulators and an enlargement of a cooling mechanism. Further, it is reported that power consumption of the modulator is reduced by filling of groove structures in the optical waveguide with a material having a large refractive index temperature coefficient with the conventional art. (For example, see Non-patent Reference 1)
Non-patent Reference 1: Yasuaki Hashizume, et al. “The Institute of Electronics, Information and Communication Engineers, General Conference, Lecture Papers, 2002,” Mar. 7, 2002, C-3-10, P14